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[`String#toCharArray`](https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/String.html#toCharArray\(\))
allocates a new array. Calling `charAt` is more efficient, because it avoids
creating a new array with a copy of the character data.
That is, prefer this:
```java
boolean isDigits(String string) {
for (int i = 0; i < s.length(); i++) {
char c = s.charAt(i);
if (!Character.isDigit(c)) {
return false;
}
}
return true;
}
```
to this:
```java
boolean isDigits(String string) {
// this allocates a new char[]
for (char c : string.toCharArray()) {
if (!Character.isDigit(c)) {
return false;
}
}
return true;
}
```
Note that many loops over characters can be expressed using streams with
[`String#chars`][chars] or [`String#codePoints`][codePoints], for example:
```java
boolean isDigits(String string) {
string.codePoints().allMatch(Character::isDigit);
}
```
[chars]: https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/String.html#chars()
[codePoints]: https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/String.html#codePoints()
|
